Certain smells can trigger seizures, though the mechanism varies depending on whether the odor acts through chemical absorption into the body or through direct stimulation of olfactory brain circuits. Essential oils containing compounds like camphor, eucalyptus (specifically 1,8-cineole), and thujone are the most thoroughly documented culprits, and strong environmental odors such as perfume and solvents have provoked seizures in people with existing epilepsy. The relationship between smell and seizure activity runs in both directions, though, because some odors appear to suppress seizures rather than cause them.
Essential Oils That Have Caused Seizures
The most consistent evidence for smell-related seizure risk comes from essential oils. A systematic review of essential oils and epilepsy identified several species whose oils have produced seizures in humans through both internal and topical use. The list includes sage, thuja (cedar), hyssop, eucalyptus, camphor, pennyroyal, and fennel. The active compounds responsible are 1,8-cineole, camphor, thujone, and pinocamphone.1PubMed Central. The Effects of Various Essential Oils on Epilepsy and Acute Seizure: A Systematic Review These are not obscure laboratory chemicals. Eucalyptus oil is in chest rubs, camphor is in topical pain balms, and sage oil shows up in aromatherapy products sold without any seizure warning.
A four-year prospective study across multiple medical centers documented 55 patients with essential-oil-related seizures. Of those, 22 had seizures directly induced by essential oils (meaning the oils were the primary cause), while 33 had seizures provoked in the context of pre-existing epilepsy. The oils most frequently implicated were preparations containing eucalyptus and camphor.2PubMed. Essential oil related seizures (EORS): A multi-center prospective study on essential oils and seizures in adults That distinction matters: some of these patients had no prior seizure history, meaning the oil exposure alone was enough.
Emergency cases reinforce this. A small case series described patients arriving in status epilepticus, a life-threatening condition of continuous seizure activity, after exposure to eucalyptus oil. Two cases involved ingestion, but a third involved only topical application of balms containing eucalyptus and camphor.3PubMed Central. Essential oil-related status epilepticus: A small case series study Topical application means the compounds were absorbed through the skin and reached the brain at high enough concentrations to cause prolonged seizure activity, not just a brief event.
How Proconvulsant Compounds Work in the Brain
The key compound in eucalyptus oil, 1,8-cineole, has a mechanism similar to pentylenetetrazole, a drug researchers deliberately use to induce seizures in lab animals. Animal studies suggest 1,8-cineole disrupts the normal sodium and potassium balance across brain cell membranes, making neurons fire more easily than they should. Research on nerve cells found that the excitatory effect is likely driven by direct blockade of potassium channels. Camphor appears to work through a similar pathway, blocking potassium channels while also increasing inward calcium currents, both of which push neurons toward hyperexcitability.3PubMed Central. Essential oil-related status epilepticus: A small case series study
This is worth understanding because it means the seizure risk from these oils is not primarily about “smelling” them in the everyday sense. When eucalyptus oil is rubbed on the chest or swallowed, the compound enters the bloodstream and acts directly on brain tissue. Inhalation of concentrated vapors can also deliver meaningful doses. The route of exposure matters for the level of risk: ingestion is the most dangerous, concentrated topical application comes next, and casual inhalation of dilute ambient scent is the least likely to cause trouble. But all three routes have been associated with seizures in documented cases.
When Pure Smell Alone Triggers a Seizure
Separate from chemical toxicity, there is evidence that olfactory nerve stimulation itself, the raw act of smelling, can trigger seizures in certain conditions. This has been demonstrated most dramatically in genetically engineered mice designed to have olfactory neurons that fire in lockstep. When these mice were exposed to octanal (an aldehyde with a citrus-like scent), some experienced full tonic-clonic seizures within 15 to 20 seconds. At higher concentrations, both the number of mice affected and the severity of their seizures increased.4PLOS ONE. A Smell That Causes Seizure
These mice are not a perfect stand-in for humans, but the experiment revealed something relevant to everyone: seizures occurred only when the smell hit suddenly. When the same concentration was delivered as a slow gradient over four minutes, no seizures occurred at all, even though roughly the same number of olfactory nerve cells were activated. The difference was that gradual exposure gave the brain’s inhibitory circuits time to keep up with the incoming signal, while sudden exposure overwhelmed them.4PLOS ONE. A Smell That Causes Seizure The takeaway is that how quickly a strong odor reaches the nose may be as important as what the odor is.
In humans, the clearest documented case of smell alone triggering seizures comes from a man with limbic encephalitis (autoimmune inflammation affecting the temporal lobe). His seizures were repeatedly provoked by intense smells, particularly his wife’s perfume. During monitored video-EEG testing, researchers had him sniff perfume, alcohol, and solvents, and each consistently triggered his typical seizures. The events lasted anywhere from 20 seconds to two minutes and arose from both temporal lobes.5Seizure. Olfactory stimulus-induced temporal lobe seizures in limbic encephalitis His brain disease made the temporal lobe abnormally excitable, and olfactory input was enough to push it past the threshold.
Olfactory Auras and Food-Related Seizures
Some people with focal epilepsy experience the relationship between smell and seizures from the other direction: the seizure itself produces a phantom smell. These olfactory auras, where a person perceives an odor that is not physically present, occur in a subset of people whose seizures originate in the mesial temporal lobe.6PubMed. Might the olfactory bulb be an origin of olfactory auras in focal epilepsy? The smell is typically unpleasant and hard to describe, often characterized as burnt or chemical-like. For the person experiencing it, the phantom odor serves as a warning that a larger seizure is about to follow.
There is also a phenomenon called eating epilepsy, where seizures are triggered by the sight or smell of food. Brain imaging and EEG recordings in these patients show discharges in the frontal and temporal lobes, the regions that process both olfactory input and the anticipation of eating.7PubMed. Understanding the pathophysiology of reflex epilepsy using simultaneous EEG-fMRI Eating epilepsy is rare, but it illustrates how deeply smell is wired into brain circuits that can become seizure-prone. The olfactory system has unusually direct connections to the limbic structures involved in epilepsy, with fewer relay stops between the nose and the temporal lobe than any other sense.
Why Children Face Greater Risk from Essential Oils
Young children are more vulnerable to essential-oil-related seizures for straightforward reasons: their body mass is smaller, so a given dose produces higher blood concentrations, and their blood-brain barrier is still maturing. New Zealand’s medicines safety authority highlighted a case in which a four-year-old girl experienced vomiting, lethargy, and loss of coordination followed by a grand mal seizure after being treated with an over-the-counter head lice product containing eucalyptus oil.8Medsafe. Essential oils associated with seizures The product was applied topically, not ingested. Healthcare professionals have been specifically warned that eucalyptus, camphor, and related essential oils can cause seizures in young children and in patients with epilepsy even when used externally.
Parents who use essential oil diffusers, vapor rubs, or “natural” remedies around young children should be aware that the concentration reaching a small child’s brain is proportionally much higher than what an adult would experience from the same exposure. Products marketed as natural are not necessarily safe for pediatric use, and the word “aromatherapy” can obscure the fact that these are pharmacologically active chemicals with real neurological effects.
Smells That May Prevent or Abort Seizures
The same olfactory pathways that can trigger seizures under some conditions appear capable of suppressing them under others. Lavender essential oil, which is rich in a compound called linalool, has shown strong anticonvulsant effects in animal studies. In one experiment, inhaled lavender oil administered before a seizure-inducing drug prevented all convulsions and produced a 100% survival rate, while every animal in the untreated group seized and died.9PubMed Central. Aromatherapy for the brain: Lavender’s healing effect on epilepsy, depression, anxiety, migraine, and Alzheimer’s disease Linalool appears to work by interfering with glutamate signaling in the brain, acting as a competitive antagonist at glutamate receptors and delaying or blocking seizures caused by compounds that activate those receptors.10PubMed. Anticonvulsant properties of linalool in glutamate-related seizure models
Beyond specific chemical effects, the raw sensory impact of a strong smell on olfactory brain regions can itself interrupt seizure activity. In rats with electrically kindled seizures originating in the amygdala (a deep brain structure involved in both emotion and epilepsy), exposure to strong odors like toluene and ammonia suppressed seizures even when the electrical stimulation was cranked to 20% above the normal seizure threshold. The odors raised the seizure threshold by about 25% compared to control conditions.11PubMed. Strong olfactory stimulation reduces seizure susceptibility in amygdala-kindled rats Later work confirmed these findings, showing that intense olfactory stimulation blocked seizures in already-kindled animals.12PubMed. Intense olfactory stimulation blocks seizures in an experimental model of epilepsy
The likely explanation involves the piriform cortex, a smell-processing region that sits at a critical junction in the brain’s limbic circuitry. Strong olfactory input floods this area with organized sensory activity, which appears to compete with and disrupt the chaotic electrical patterns of a seizure. It is a form of sensory interference: the brain cannot sustain its abnormal seizure discharge while simultaneously processing a powerful, legitimate sensory signal through the same circuits.
The “Shoe-Smell” Folk Practice
In parts of South and Southeast Asia, a traditional first-aid response to witnessing someone having a seizure is to hold a worn shoe near the person’s nose. This practice has persisted for generations, and researchers have investigated whether there is any neurological basis for it. A study examining the neurophysiology of olfactory stimulation during seizure activity found that strong olfactory stimuli did possess a meaningful anti-epileptic influence, which the authors argued could explain both the origin and the persistence of the shoe-smell practice in developing regions.13PubMed. Scientific basis behind traditional practice of application of “shoe-smell” in controlling epileptic seizures in the eastern countries
The idea is not that shoe leather contains a specific anticonvulsant compound. Rather, a worn shoe produces a pungent, complex odor that delivers intense stimulation to both the olfactory nerve and the trigeminal nerve (the nerve responsible for detecting irritants and sharp chemical sensations). That dual activation may be what gives the practice whatever effect it has. It is consistent with the animal research showing that strong, potentially irritating smells like ammonia and toluene are the most effective at raising seizure thresholds. A pleasant, mild scent would not deliver the same sensory punch.
Trigeminal Versus Olfactory Nerve Activation
Not all “smells” stimulate the same nerves. Pure olfactory stimulants like vanillin (the smell of vanilla) activate the olfactory nerve and produce brain responses centered in the parietal and central regions, spread fairly evenly across both hemispheres. Irritant chemicals like ammonia and sulfur dioxide additionally activate the trigeminal nerve, which produces a different pattern: brain responses centered at the vertex (top of the head) and stronger on the side opposite the stimulated nostril.14Electroencephalography and Clinical Neurophysiology/Evoked Potentials Section. Differences in human evoked potentials related to olfactory or trigeminal chemosensory activation
This distinction matters for understanding both seizure triggering and seizure suppression. A smell that activates only the olfactory nerve sends its signal through the olfactory bulb and directly into the temporal lobe. A smell that also activates the trigeminal nerve recruits a broader network. For seizure suppression, the trigeminal component may be the more important one, because it engages brainstem pathways that can modulate arousal and cortical excitability. For seizure triggering, the olfactory pathway’s direct line into the temporal lobe is the more concerning route, especially in people whose temporal lobes are already primed to seize.
The Olfactory Bulb’s Role in Epilepsy Research
The olfactory bulb, the first relay station for smell signals entering the brain, has become a useful tool in epilepsy research precisely because of its tight connections to seizure-prone brain areas. Electrical kindling of the olfactory bulb in rats produces a reliable model of limbic epilepsy, the type of epilepsy that originates in the temporal lobe and hippocampus.15PubMed. Kindling and electrode effects on the benzodiazepine receptors density of olfactory bulb and hippocampus after olfactory bulb kindling Studies using this model have shown that repeated stimulation of the olfactory bulb causes synaptic remodeling and neuronal degeneration in the hippocampus and piriform cortex, the same structural changes seen in human temporal lobe epilepsy.16PubMed. Synaptic degeneration and remodelling after fast kindling of the olfactory bulb
This model has practical value beyond basic science. Olfactory bulb kindling develops rapidly and responds to standard anti-epileptic drugs, making it a useful screening tool for evaluating new seizure medications.17PubMed. The usefulness of olfactory bulb kindling as a model for evaluation of antiepileptics The fact that the olfactory system can so easily become an engine for seizure generation underscores something about human brain anatomy that most people do not appreciate: the nose has an unusually short and powerful connection to the parts of the brain most vulnerable to epilepsy.
Practical Considerations for People with Epilepsy
If you have epilepsy or care for someone who does, the evidence suggests a few concrete precautions worth considering:
- Eucalyptus and camphor products: Vapor rubs, topical balms, and concentrated eucalyptus oil carry the most documented risk. This applies to both ingestion and skin application, not just inhalation. If you have epilepsy, discuss use of these products with your neurologist.
- Essential oil diffusers: Diffusing sage, hyssop, or rosemary oils in enclosed spaces can produce meaningful vapor concentrations. The risk is higher for children and for adults with known seizure disorders.
- Sudden strong odors: Animal research consistently shows that sudden onset of a strong smell is more likely to affect brain activity than gradual exposure to the same concentration. If you notice that strong, abrupt smells seem to precede your seizures, mention it to your doctor, as this could indicate a reflex component to your epilepsy that might change how it is managed.
- Olfactory auras: If you smell something burning, chemical, or otherwise unpleasant that no one else notices, especially if it happens repeatedly and is followed by confusion or loss of awareness, this may be an olfactory aura from a temporal lobe seizure rather than an environmental odor. It is worth reporting to a neurologist even if the episodes seem brief.
The evidence for smell-based seizure suppression, while intriguing in animal models, is not yet strong enough to recommend as a clinical strategy for humans. Lavender oil and linalool show genuine anticonvulsant properties in controlled laboratory settings, but translating that into reliable advice for a person having a seizure is a different matter entirely. No clinical trial has demonstrated that sniffing lavender during a seizure aura reliably prevents progression. Some epilepsy centers are investigating olfactory countermeasures, but for now, standard rescue medications remain the evidence-based first response.
How Olfactory Monitoring Works in the Clinic
When a neurologist suspects that smells may be triggering a patient’s seizures, the diagnostic approach typically involves video-EEG monitoring with deliberate olfactory provocation. The limbic encephalitis patient whose seizures were triggered by perfume and solvents was tested this way: researchers presented specific odors under controlled conditions while recording brain electrical activity in real time, confirming that the olfactory stimuli consistently produced seizure discharges from the temporal lobes.5Seizure. Olfactory stimulus-induced temporal lobe seizures in limbic encephalitis Protocols for olfactory stimulation during EEG monitoring have been designed to avoid the confounding effect of olfactory adaptation, where nerve cells become less responsive to a sustained odor. This is accomplished by intermittently approaching and withdrawing the odor source rather than holding it steady under the nose.18Epilepsy & Behavior. Olfactory stimulation induces delayed responses in epilepsy
Identifying a specific olfactory trigger can have real clinical value. If a particular class of chemicals reliably provokes seizures in a given patient, avoidance becomes a targeted strategy rather than a vague recommendation. It also helps classify the epilepsy syndrome, since reflex epilepsies triggered by sensory stimuli sometimes respond differently to medications than spontaneous seizures. In rare cases, identifying the trigger has led to meaningful seizure reduction through environmental modification alone, though most patients still need pharmacological treatment as well.